# Surface Waves of an Oil Ocean

1. Feb 8, 2009

### lewdtenant

I'm interested in the physical behavior of surface waves in an oil-based ocean.

Suppose, if you will, an ocean created of crude oil. How would its waves behave in relation to our own oceans' waves?

I think oil waves would be slower and lower in height, but how much slower and lower I don't know. I'm sure there are other characteristics to consider as well. Care to speculate?

2. Feb 8, 2009

### Cyrus

(1) Get a house fan
(2) Get a cat liter box
(3) Fill said box with water. Turn on fan. Take Picture
(4) Empty box, and refill with motor oil. Turn on fan, take picture.
(5) Using a funnel, put motor oil back into the container for use in your car when in need of top off.

(6) Post pictures here.

3. Feb 8, 2009

### lewdtenant

...but I'm a theorist...

ok I thought of doing an experiment myself... i guess i have to now

4. Feb 8, 2009

### skeptic2

Slightly off topic anecdote:

When Ben Franklin was a diplomat to France, once he was walking close to a body of water with two Frenchmen on a windy day. Always having a keen sense of humor and an interest in science he told the Frenchmen to step back, he was going to calm the waters. Franklin was carrying a hollow cane he had filled with oil beforehand. He unstoppered the cane and waved it over the water and behold, the waters were calmed. The Frenchmen were duly impressed.

5. Feb 8, 2009

### Cyrus

Hahahha! That Franklin guy was a clever. I would expect nothing less from him!

6. Feb 8, 2009

### lisab

Staff Emeritus
OK...so who walks around with a hollowed-out cane filled with oil?

7. Feb 8, 2009

### rootX

Google might provide some quantitative data.

8. Feb 8, 2009

### Cyrus

My freshman undergraduate physics text book doesnt have the answer, so why would a grade 11 physics book have it?

Surface roughness is a complex phenomenon that depends on many things, including the surface under the water. The water has ripples and waves in different parts of the lake due to different ground textures.

You could also test this in your litter box. Fill it with water and turn on the fan. Then fill the bottom with gravel and repeat. You will get a different wave pattern.

9. Feb 9, 2009

### BobG

A person that had already observed the phenomenon created when cooks on sailing ships dumped their grease overboard. The wakes left behind those ships were much smoother than the wakes of other ships (the ship he was on was part of a fleet of 96 British ships sailing against the French, so the two ships with smooth wakes was definitely noticeable, with the explanation provided by the captain of the ship he was on).

The whole intention of carrying the oil with him was so he could perform his own experiments whenever the opportunity arose.

The honour of Dutch seamen: Benjamin Franklin’s theory of oil on troubled waters and its epistemological aftermath

Edit: skeptic2's anecdote wasn't off topic, at all.

Last edited: Feb 9, 2009
10. Feb 9, 2009

### rootX

Neither my freshman physics book has the answer. But, I remember gr 11 physics book talking about how material properties/density or ocean depth affect the waves speed etc. It wasn't in detail and explanations were overly simplified. I don't think it ever considered under water surface textures.

I am done all undergrad physics courses but never saw anything about surface waves.

11. Feb 9, 2009

### skeptic2

Thanks BobG. I had remembered it as happening in France. I guess I was mistaken.

12. Feb 9, 2009

### BobG

I believe he demonstrated the oil on the water experiment several places, including France.

13. Feb 9, 2009

### minger

A quick google shows that an ocean wave travels at:
$$v = \sqrt{ \frac{g\lambda}{2\pi} \tanh\left(\frac{2\pi d}{\lambda}\right)}$$
Where v is the velocity, $$\lambda$$ is the wavelength of the traveling wave, d is the water depth, and g is gravity. It seems independent of fluid density.

This is counter-intuitive to my initial thinking, which relates to speed of propagating sound waves. The speed of sound can be written as:
$$c = \sqrt{\gamma \frac{p}{\rho}}$$
Where p is pressure and $$\rho$$ is the fluid density. An increase in fluid density in sound waves decreases the speed of sound.

However, it seems as though from a few sources that the speed is a function of wavelength only. http://www.owrc.com/waves/waves.html [Broken]

Last edited by a moderator: May 4, 2017
14. Feb 9, 2009

### physics girl phd

Don't ever say this! The wavelength is determined by two things: The frequency of the source of the wave, and the speed of the wave in the material (determined by material properties... which CAN sometimes be a function of frequency, as dispersion). The equation v=f*lamba is in my opinion one of the worst mathematical statements commonly seen in physics texts. lamda = v/f would be so much better.

Wavelength never determines speed. It's always better to think of any wave in terms of its frequency rather than its wavelength... because the frequency (usually) doesn't change. I'll state "usually" because of certain things like harmonic generation, etc.

Last edited by a moderator: May 4, 2017